Best Way to set the idle mix on a 4160

[DanEC]

You can set the idle mixture with a vacuum gage or a tach. I've gotten to where I prefer a tach in recent years but I still use a vacuum gage sometimes. You should tune each side to achieve the highest vacuum or idle rpm separately - going back and forth a couple of times. On most motors the adjustments will end up pretty close to each other - but yeah, there may be a little difference in where the screws end up from side to side.

[steve meltzer]

thanx so much. that's what i suspected...max vac. s

[patrickt]

If you're between 3/4's of a turn out and 1-1/2 turn out the car should run decently. You can also try the old trick of adjusting the turns so that when you pull the rubber plug off the intake manifold port the RPM's stay the same. The most important part is not to have your idle turned up so far that you're too deep in to the transition slot. Or, you can do what I do to get it just perfect......... Make sure your primary butterflies are at the bottom of the transition slot, back your idle screws out about 3/4's of a turn from seated, then adjust the idle speed by cracking the secondaries with the hidden set screw. Then take your car out for a steady slow drive with the throttle lightly applied and steady and feel for your lean surge, which you should have. Back the screws out 1/8th of a turn and repeat until the surge is gone. The object is to have the leanest possible idle mixture setting that allows the car to run nicely.

[steve meltzer]

Patrick, i know we talked about replacing the factory slotted screw for the idle on the secondary. did you use a socket cap (with hex for an Allen key) or what? 1/4-20 or? thanx. steve

[patrickt]

Originally Posted by steve meltzer

Patrick, i know we talked about replacing the factory slotted screw for the idle on the secondary. did you use a socket cap (with hex for an Allen key) or what? 1/4-20 or? thanx. steve

10-32 cap screw. For use with an Allen wrench.

[steve meltzer]

thanx. s

[steve meltzer]

ooops! tryin' to have them on hand in advance...gotta length? now, i think, i'll stop pestering you. (temporarily!) s